A study published in Nature and Science of Sleep contends that “continued indiscriminate use of the apnea-hypopnea index (AHI) should be discouraged.” Instead, researchers suggest that numerous alternative measures be incorporated to provide the total sleep picture.
Determining exactly what is being counted during the AHI is thoroughly examined, with researchers concluding that “it is inconceivable that all apneas and all hypopneas are the same kind of exposure, as far as effects are concerned. For instance, the clinical consequences of not breathing for 60 seconds cannot be identical to the consequences of shallow breathing for 30 seconds, and the consequences of accompanying hypoxemia surely depend on its magnitude and duration, not on an arbitrary cutoff point.”
Many of the arguments and/or alternative measures presented presented in the full study extend to other ratio variables that are commonly used in sleep research, such as the arousal index, percentage of time in desaturation, and percentage of time in each sleep stage. “In fact, the modeling of ratios has been harshly criticized in other branches of science as well,” write researchers.
“However, the lessons offered are far more general. First, a variable that is useful in clinical practice is not necessarily the preferred variable in biomedical science. Second, we should never accept a new variable into science on the basis of feelings or authority. Third, if the analyzed variable is a derived variable, researchers should explicitly state which natural variable they claim to be measuring. And if they are unwilling to commit to a clear theory, they are not in the business of science.”